They also face charges of entering Kenya illegally and obtaining false identification documents.

All the gunmen in the Westgate siege -- totalling just four, not the dozen that security forces initially reported -- are understood to have died during the attack.

The four-day attack in the upmarket shopping centre was claimed by Somalia's Al-Qaeda-linked Shebab. They said it was a warning to Kenya to pull its troops out of southern Somalia, where they are fighting the extremists as part of an African Union force.

Interpol and the FBI have been assisting Kenya in trying to identify four bodies believed to be those of the attackers.

Two of the gunmen -- who the four are accused of supporting -- are named in court documents as Mohammed Abdinur Said and Hassan Abdi Dhuhulow, a 23-year-old Somali who spent time in Norway.

Like the attackers, the four suspects are all ethnic Somalis, but it is unclear whether they are Somali or Kenyan citizens.

The four are due to appear in court for a hearing on December 18, but their trial is not expected to begin in earnest until mid-January.

Western sources familiar with the investigation suggest the evidence concerning the suspects is credible enough to warrant a trial.

Witnesses in the mall described how the fighters stormed the crowded complex, firing from the hip and hurling grenades at shoppers and staff.

Kenya's Red Cross say that at least 20 more people are still missing, with Western officials suggesting that as many as 94 could have died in total in the attack, with some victims still potentially remaining under tonnes of rubble after part of the mall's roof collapsed at the end of the raid.